[PATCH 5.14 050/849] ext4: refresh the ext4_ext_path struct after dropping i_data_sem.

Greg Kroah-Hartman
2021-11-16T01:47:17Z

From: yangerkun <yangerkun@huawei.com>

commit 1811bc401aa58c7bdb0df3205aa6613b49d32127 upstream.

After we drop i_data sem, we need to reload the ext4_ext_path
structure since the extent tree can change once i_data_sem is
released.

This addresses the BUG:

[52117.465187] ------------[ cut here ]------------
[52117.465686] kernel BUG at fs/ext4/extents.c:1756!
...
[52117.478306] Call Trace:
[52117.478565] ext4_ext_shift_extents+0x3ee/0x710
[52117.479020] ext4_fallocate+0x139c/0x1b40
[52117.479405] ? __do_sys_newfstat+0x6b/0x80
[52117.479805] vfs_fallocate+0x151/0x4b0
[52117.480177] ksys_fallocate+0x4a/0xa0
[52117.480533] __x64_sys_fallocate+0x22/0x30
[52117.480930] do_syscall_64+0x35/0x80
[52117.481277] entry_SYSCALL_64_after_hwframe+0x44/0xae
[52117.481769] RIP: 0033:0x7fa062f855ca

Cc: stable@kernel.org
Link: https://lore.kernel.org/r/20210903062748.4118886-4-yangerkun@huawei.com
Signed-off-by: yangerkun <yangerkun@huawei.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/ext4/extents.c | 14 +++++++++++++-
1 file changed, 13 insertions(+), 1 deletion(-)

--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -5006,8 +5006,11 @@ ext4_ext_shift_path_extents(struct ext4_
restart_credits = ext4_writepage_trans_blocks(inode);
err = ext4_datasem_ensure_credits(handle, inode, credits,
restart_credits, 0);
- if (err)
+ if (err) {
+ if (err > 0)
+ err = -EAGAIN;
goto out;
+ }

err = ext4_ext_get_access(handle, inode, path + depth);
if (err)
@@ -5081,6 +5084,7 @@ ext4_ext_shift_extents(struct inode *ino
int ret = 0, depth;
struct ext4_extent *extent;
ext4_lblk_t stop, *iterator, ex_start, ex_end;
+ ext4_lblk_t tmp = EXT_MAX_BLOCKS;

/* Let path point to the last extent */
path = ext4_find_extent(inode, EXT_MAX_BLOCKS - 1, NULL,
@@ -5134,11 +5138,15 @@ ext4_ext_shift_extents(struct inode *ino
* till we reach stop. In case of right shift, iterator points to stop
* and it is decreased till we reach start.
*/
+again:
if (SHIFT == SHIFT_LEFT)
iterator = &start;
else
iterator = &stop;

+ if (tmp != EXT_MAX_BLOCKS)
+ *iterator = tmp;
+
/*
* Its safe to start updating extents. Start and stop are unsigned, so
* in case of right shift if extent with 0 block is reached, iterator
@@ -5167,6 +5175,7 @@ ext4_ext_shift_extents(struct inode *ino
}
}

+ tmp = *iterator;
if (SHIFT == SHIFT_LEFT) {
extent = EXT_LAST_EXTENT(path[depth].p_hdr);
*iterator = le32_to_cpu(extent->ee_block) +
@@ -5185,6 +5194,9 @@ ext4_ext_shift_extents(struct inode *ino
}
ret = ext4_ext_shift_path_extents(path, shift, inode,
handle, SHIFT);
+ /* iterator can be NULL which means we should break */
+ if (ret == -EAGAIN)
+ goto again;
if (ret)
break;
}